1. Field of the Invention
This invention relates to a safety system for a firearm, and more particularly to an electromechanical safety system accessible to an authorized user only.
2. Description of the Related Art
With 16 children on average being killed in the United States every day by a firearm, there is an obvious and compelling need to make firearms operable by only those individuals authorized to use them.
External trigger locks fitting around the trigger and preventing the use of the firearm have long been offered as one solution. That approach has proven to be ineffective for several reasons:                the trigger locks have trouble fitting effectively around the myriad of trigger guards;        not all firearms have trigger guards;        trigger locks cannot be used to lock a loaded firearm;        those that use a key generally end up being stored with the key hidden nearby;        many can be easily disabled with common hand tools; and        the average firearm owner does not think he can find the key or remember the combination, unlock the trigger guard, and load the weapon in the dark in a short enough time to defend himself from an intruder.        
Others have approached the problem by:
using radio signals to energize a solenoid to block the trigger (U.S. Pat. No. 5,168,114 issued to Enger on Dec. 1, 1992); or
using the interaction with a passive electronic circuit worn on the body of an individual to energize a motor or solenoid within the firearm by either having that electronic circuit detected by an electronic energy field in the firearm, or by generating an authorizing signal or code in short wave. (U.S. Pat. No. 4,488,370 issued to Lemelson on Dec. 18, 1984); or
using a magnetized ring or microchip bearing ring coming within the range of a decoder on the firearm which generates an electronic signal to energize a solenoid to activate or deactivate the firearm. (U.S. Pat. No. 5,016,376 issued to Pugh on May 21, 1991); or
using a code generator such as a microchip or bar code, worn on the finger or the palm of the hand which is read by a detector in the handgun, which in turn will actuate or deactuate a solenoid. (U.S. Pat. No. 5,062,232 issued to Eppler on Nov. 5, 1991); or
using an external keypad as an electronic key by connecting it to an electronic decoder unit on the handle of the firearm which then energizes a motor to rotate an aperture in a gear which will either allow the main spring rod of the firearm to be moved to a position to be actuable by the trigger, or will prevent it from so doing. The main spring rod is connected to the hammer and controls the release of the hammer to strike the cartridge. (U.S. Pat. No. 5,022,175 issued to Oncke on Jun. 11, 1991); or
using an audio receiver on the firearm to recognize and respond to audio frequency signals such as a word or words authorizing an element to block the backward movement of the trigger. (U.S. Pat. No. 5,546,690 issued to Ciluffo on Aug. 20, 1996).
With the exception of the aforesaid Ciluffo patent, all of the above approaches require the use of an identifying and/or authorizing device external to the firearm. As a practical matter, while a police officer may on a daily basis, carry or wear as part of his equipment, a key, magnet, radio transmitter, specialized electronic circuit, or some such other device, the average firearm owner will not. Accordingly, safety systems relying on such an approach will not likely be in demand and will not be commercially feasible.
The efficacy of a voice recognition approach, as suggested by the aforesaid Ciluffo patent, is limited by the ability of voice recognition devices to reliably distinguish one particular voice from another, as well as by the large amount of electric power necessary to operate a voice recognition system of that sort with any kind of consistency.
Additionally, since firearms in general, and handguns in particular, are significantly lacking in available space for any additional modifications, any safety system that relies in part on the use of a solenoid is not likely to be commercially feasible due to the necessarily large size of a solenoid, as well as the attendant huge demand for power to drive a solenoid. Solenoids require a substantial surge of power for initial activation, as well as the constant application of power to remain activated. Battery operated solenoids will run the risk of total or partial failure. An electronic safety system that does not work on demand or runs the risk of limited success will not be marketable. In the world of firearms, the system cannot work just “most of the time”; it must work every time.
Lastly, while it may seem attractive to place things in the grip of a firearm, as suggested by much of the prior art, generally speaking, the grip cannot be expanded much, if at all, without making it too large for an individual to hold and still reach the trigger with the first joint of the index finger. Any device or system that requires the modification of the grip to accommodate items having more than minimal volume may very well result in that firearm being nonusable and nonmarketable.